1. Field of the Invention
The present invention relates to a porous photosensitive body used for an image recording device such as a copying machine, facsimile, printer or a like and to a method for manufacturing same.
2. Description of the Related Art
As technology of forming an image, for example, in a copying machine, electronic printing technologies including a Carlson process (one of the xerographic methods) are known. In the Carlson process, since printing is made by six processes of charging, exposure, development, transfer, fixation and cleaning and since a unit is to be used specifically for each of the six processes is required, increased size of a printing device, generally, is unavoidable.
To solve this problem, electronic printing technology to substitute as the Carlson method has been disclosed by the applicant of the present invention in Japanese Patent Application Laid-open No. Hei9-204092. FIG. 19 is a perspective view showing configurations of a porous photosensitive body disclosed in the above patent application. As shown in FIG. 19, a porous photosensitive body 192 is composed of a large number of fine holes 191a opening on a surface of a layer and an insulating layer 191 having an electrode 191b exposed toward an outside which is stacked on a cylindrical body (not shown) used for forming the porous photosensitive body, wherein each of the fine holes 191a is filled with conductive coloring grains (toners) on which exposure light corresponding to printing information is irradiated to cause the photosensitive coloring grains to hop and to be selectively transferred through paper to be printed to an electrode 191b disposed in an opposed direction at a time of printing. A rotary axis 193 is provided with a flange 193a and is rotated in a main scanning direction xe2x80x9caxe2x80x9d or in a sub-main scanning direction xe2x80x9cbxe2x80x9d. By configuring the porous photosensitive body as above, the printing can be completed by three processes including filling with coloring grains, exposure and grain hopping and fixing, thus allowing a printing device to be made compact as a whole. Preferably, the porous photosensitive body is of a cylindrical shape or of a jointless sheet shape so that consecutive printing can be performed. Planar shape of the fine holes 191a can be round, elliptical, square or honeycomb, whichever may be selected as necessary.
In the porous photosensitive body of this type, to ensure a predetermined image density at the time of printing, a depth of each of the fine holes 191a constituting a minimum print unit (one dot), that is, a thickness of the insulating layer 191 is set so as to be comparatively large, while to ensure an image with high resolution, a pitch between two fine holes 191a being adjacent to each other is set to be as small as possible.
To fabricate the porous photosensitive body of this type, there is conventionally a method in which a sheet composed of an insulating body having the large number of fine holes 191a is wound around a circumferential face of the drum used to form the porous photosensitive body. However, in this method, a joint of the sheet is produced after the sheet is wound, which causes a defect in the image, resulting in reduction in quality of the printed image.
Moreover, there is another method for fabricating the porous photosensitive body of this type, in which, after insulating layers are formed on a circumferential face of a cylindrical drum for forming a photosensitive body, a large number of fine holes are made on an insulating body by using a laser or a drill. However, it is impossible to use this method practically, because only one hole can be made by a one time hole-making operation. For example, when printing with a resolution of 200 dots/inch is to be performed on A4 size paper, a million or more fine holes to be made on the insulating layer of the cylindrical drum with 210 mm in length and 30 mm in diameter are required. Though the large number of fine holes 191a can be made also by using the laser, thereby providing a high quality of printed images, is difficult to mass produce and is costly.
To handle these problems, a further method for fabricating the porous photosensitive body is proposed, in which an insulating layer made of a photo-curing liquid resin having cured and non-cured portions corresponding to hole patterns is stacked on a photo-conductive layer from which the non-cured portions have been removed. An insulating layer 201 is formed by such a method as shown in FIG. 20 which is a cross-sectional view of the conventional porous photosensitive body. That is, as shown in FIG. 20, a translucent conductive layer 203 and photo-conductive layer 204 are stacked, in consecutive order, on a circumferential face of a cylindrical translucent supporting body 202 and then a photo-curing liquid resin is coated on a circumferential face of the drum 205 (stacked body).
Moreover, as shown in FIG. 20, a pattern of a fine holes 201a of the insulating layer 201 is formed by irradiating exposure light along an axial direction while the drum 205 having the insulating layer 201 is being rotated at an angle xcex8 corresponding to a hole pitch in a circumferential direction. Also, as shown in FIG. 20, the porous photosensitive body 206 is made of the drum 205 having the insulating layer 201 and 4 surface electrode 207.
However, the porous photosensitive body obtained by the methods described above has the following problems:
(1) Because the printing is made by irradiating exposure light from an exposure system (not shown) mounted in the cylindrical translucent supporting body 202, that is, the printing is made by a rear exposure printing method, the translucent supporting body 202 must be formed with high accuracy and therefore this method is not suitable for the mass production thereof.
(2) To achieve the printing with high resolution, it is necessary to perform a highly accurate alignment for a single line or several lines along the axial line of the cylindrical drum. This is because, unless the highly accurate alignment is performed, due to errors in angles occurring in one step being accumulated for each rotation of the drum at the time of exposure, a pitch between an exposure starting end and an exposure terminating end is not matched to one between fine holes 201a which causes a portion not to be exposed to be exposed and, due to curing of the resin in this portion, a line in which the fine hole 201a is not formed in the direction of the axial line of the drum, that is, a joint is produced. As a result, such additional devices as an angle detecting device, position detecting device or a like are required, which makes costs high.
(3) The fine hole 201a (FIG. 20) is formed, as shown by FIG. 21, by irradiating exposure light corresponding to a hole pattern on an photo-curing liquid resin 211, which constitutes the insulating layer 201 shown in FIG. 20, to cause a cured resin portion 211a and a non-cured resin portion 211b (a portion to produce a latent image) to be formed and then by removing the non-cured resin portion 211b. In this method, if exposure quantity is not adjusted, as shown in FIG. 22, a portion constituting the cured resin portion 211a is expanded due to halation of the transmitted light 212a reaching a groundwork layer 213 (photo-conductive layer 204 in FIG. 20) of the photo-curing liquid resin 211, causing the aperture portion of the fine hole 201a to be partially narrowed. FIG. 23 is a graph showing a relationship between exposure quantity and hardness of the photo-curing liquid resin 211 when the exposure light is irradiated on the insulating layer 201 of the conventional porous photosensitive body 206. As shown in FIG. 23, generally, in a sensitivity curve of the photo-curing liquid resin 211, as the exposure quantity increases, the hardness of the photo-curing liquid resin 211 increases and, after the exposure quantity exceeds a threshold value, the hardness of the photo-curing liquid resin 211 increases is saturated (it reaches a specified value), in many cases. However, if the halation does not occur from the groundwork layer 213, even when more of the exposure light 212 than is required is irradiated on the photo-curing liquid resin 211, the aperture portion of the fine hole 201a is not narrowed. Actually, due to the halation, the aperture portion of the fine hole 201a is partially narrowed, thus causing an unsatisfactory formation of the fine hole 201a. Because of this, the exposure by adjusting the exposure quantity (to an exposure quantity xe2x80x9caxe2x80x9d in FIG. 23) is a good measure. However, a slope of a curve varies depending on types of photo-curing liquid resin to be used and, even in same types of the resin temperature conditions greatly influence viscosity of the photo-curing liquid resin or pot life of the photo-curing liquid resin. The slope of the curve varies depending on delicate changes in illuminance and/or wavelength caused by a quality of the exposure light 212 or a temperature of an exposure lamp. Therefore, the above adjustment of the exposure quantity required much time and causes a reduction in productivity.
(4) A proximity exposure method or projection exposure method is employed for irradiation of the exposure light on the photo-curing resin 211 to facilitate peeling of a mask after curing of the resin and to avoid defects in image at a time of peeling the mask. In these methods, the exposure light 212 is refracted due to a gap formed between a mask M (FIG. 21, FIG. 22) and photo-curing liquid resin 211 at the time of the exposure process, making it difficult to obtain an excellent degree of imageformation.
(5) Since the surface electrode 207 shown in FIG. 20 is formed by evaporation with metal or by printing of a metal paste on a surface of the insulating layer 201, its thickness is made thin and cannot be controlled so as to be uniform, causing an easy breakdown of the surface electrode 207 when used very frequently and causing its functional defects due to partial rise of a resistance (for example, because the fine hole 201a is not properly filled with the conductive coloring grains), thus resulting in reduction of reliability for use.
Other conventional porous photosensitive bodies are disclosed in Japanese Patent Application Laid-open No. Sho53-138734 and No. Sho59-185339, in which, xe2x80x9cas shown in FIG. 24, after an insulating layer 242 and conductive layer for biasing 243 are stacked on a conductive screen base body 241, a photo-conductive layer 244 is stacked on the stacked body composed of the insulating layer 242 and conductive layer 243 and the conductive screen base body 241 by using a spray methodxe2x80x9d and therefore the problems described above remains unsolved by technologies described above.
In view of the above, it is an object of the present invention to provide a porous photosensitive body being excellent for mass production and lower in production costs and capable of obtaining a good degree of image-formation and of increasing its productivity and reliability.
According to a first aspect of the present invention, there is provided a porous photosensitive body including:
a drum for forming the porous photosensitive body constructed by stacking, in order, an insulating layer, a photo-conductive layer and a translucent conductive layer on an inner circumferential face of a supporting cylinder; and
whereby the supporting cylinder is composed of a metal jointless cylinder having a large number of fine holes which are aligned at equal intervals both in a circumferential direction of the drum and in a direction of an axial line of the drum and are opened on inner and outer circumferential faces of the metal jointless cylinder and wherein the insulating layer is provided with a through hole communicating with each of the fine holes made on the metal jointless cylinder.
In the foregoing, a preferable mode is one wherein the supporting cylinder is composed of the jointless cylinder having a Vickers hardness of 50 to 1500.
By configuring as above, the supporting cylinder having enough mechanical strength to be used as a supporting body of the drum for forming the porous photosensitive body.
Also, a preferable mode is one wherein the supporting cylinder is made of the metal jointless cylinder containing nickel.
By configuring as above, the supporting body having enough corrosion resistance to be used as the supporting body can be obtained.
Also, a preferable mode is one wherein the insulating layer is made of an organic photosensitive resin.
By configuring as above, freedom to choose materials for the insulating layer is increased more when compared with a case where an inorganic photosensitive resin is used at a time of selection of materials.
Furthermore, a preferable mode is one wherein the photosensitive resin is made of a positive type photoresist. In this method, therefore, when the organic photosensitive resin is exposed, an exposed portion of the organic photosensitive resin is dissolved by a liquid developer.
According to a second aspect of the present invention, there is provided a method for manufacturing a porous photosensitive body having a drum for forming the porous photosensitive body constructed by stacking, in order, an insulating layer, a photo-conductive layer and a translucent conductive layer on an inner circumferential face of a supporting cylinder including steps of:
forming the supporting cylinder composed of a metal jointless cylinder having a large number of fine holes which are aligned at equal intervals both in a circumferential direction of the drum and in a direction of an axial line of the drum and are opened on inner and outer circumferential faces of the metal jointless cylinder; and
forming a through hole communicating with each of the fine holes before the photo-conductive layer is stacked.
According to a third aspect of the present invention, there is provided a method for manufacturing a porous photosensitive body having a drum for forming the porous photosensitive body constructed by stacking, in order, an insulating layer, a photo-conductive layer and a translucent conductive layer on an inner circumferential face of a supporting cylinder including steps of:
forming the supporting cylinder composed of a metal jointless cylinder having a large number of fine holes which are aligned at equal intervals both in a circumferential direction of the drum and in a direction of an axial line of the drum and are opened on inner and outer circumferential faces of the metal jointless cylinder; and
forming a through hole communicating with each of the fine holes after the photo-conductive layer is stacked.
According to a fourth aspect of the present invention, there is provided a method for manufacturing a porous photosensitive body having a drum for forming a photosensitive body constructed by stacking, in order, an insulating layer, a photo-conductive layer and a translucent conductive layer on an inner circumferential face of a supporting cylinder including steps of:
forming the supporting cylinder composed of a metal jointless cylinder having a large number of fine holes which are aligned at equal intervals both in a circumferential direction of the drum and in a direction of an axial line of the drum and are opened on inner and outer circumferential faces of the metal jointless cylinder; and
forming a through hole communicating with each of the fine holes after the translucent conductive layer is stacked.
In the foregoing, it is preferable that the supporting cylinder is formed by an electroplating method.
By configuring as above, the supporting cylinder having enough thickness of the supporting cylinder to be used as a surface electrode can be obtained.
Also, it is preferable that the insulating layer is made of a photosensitive resin and the fine holes are made by irradiating exposure light on the photosensitive resin to dissolve an irradiated portion.
Also, it is preferable that the irradiating exposure light is irradiated on the insulating layer through the supporting cylinder. In this method, therefore, the supporting cylinder is used as a mask at a time of exposure and the irradiating exposure light is irradiated through this mask.
Also, it is preferable that the irradiating exposure light from a mercury lamp is irradiated on the insulating layer. In this method, therefore, the supporting cylinder is used as the mask and the irradiating exposure light from the mercury lamp is irradiated through this mask.
Also, it is preferable that the irradiated portion is dissolved by dipping a stacked body formed by stacking the insulating layer on the inner circumferential face of the supporting cylinder in a solvent. In this method, therefore, when the stacked body is dipped into a solvent after the irradiating exposure light is irradiated on the insulating layer, the irradiated portion of the insulating layer is dissolved and becomes the fine hole.
Also, it is preferable that the irradiated portion is dissolved by spraying the solvent on the insulating layer. In this method, therefore, when the solvent is sprayed after the irradiating exposure light is irradiated on the insulating layer, the irradiated portion of the insulating layer is dissolved and becomes the fine hole.
Also, it is preferable that the insulating layer or the photo-conductive layer is stacked by dipping each body to be stacked into a resin material. In this method, therefore, when the supporting cylinder is dipped in the resin material, the insulating layer is stacked and when the stacked body is dipped in the resin material, the photo-conductive layer is stacked onto the insulating layer and then onto the supporting cylinder.
Also, it is preferable that the insulating layer or the photo-conductive layer is stacked by applying the resin material to each body to be stacked and then by rotating each body to be stacked. In this method, therefore, when the supporting cylinder coated with the resin material for forming the insulating layer, the insulating layer is stacked onto the supporting cylinder and when the stacked body formed by coating the insulating layer with the resin material for forming the photo-conductive layer is rotated, the photo-conductive layer is stacked through the insulating layer onto the supporting cylinder.
Also, it is preferable that baking treatment is performed on each resin material when the insulating layer or the photo-conductive layer is stacked. In this method, therefore, the insulating layer or photo-conductive layer is stacked, in a state where the insulating layer or photo-conductive layer is solidified by baking them on each resin material, on each body to be stacked.
Also, it is preferable that a surface of the supporting cylinder is coated when the insulating layer or the photoconductive layer is stacked.
By configuring as above, adhesion of the resin material to the surface of the supporting cylinder can be prevented when the insulating layer or photo-conductive layer is stacked.
Furthermore, it is preferable that the translucent conductive layer is stacked by applying a liquid material to an inner circumferential face of the photo-conductive layer and by curing. In this method, therefore, the translucent conductive layer is obtained in a state where liquid resin is applied to the inner circumferential face of the photo-conductive layer and is cured.